Astrophile: Two craters that launched 1000 meteoroids

HELEN of Troy was the face that launched 1000 ships. Meet Rheasilvia and Veneneia, the asteroid craters that launched 1000 meteorites.

Meteoroids form when one asteroid or planet hits another, turfing out rocks that become known as meteorites if they ever land on Earth. Astronomers had suspected for decades that Vesta, the solar system's second-biggest asteroid, was the source of the HED meteorites - about 1000 of which have been found on Earth.

Now new images from NASA's Dawn spacecraft, which has been orbiting Vesta since July last year and has mapped nearly 80 per cent of its surface, are filling in the details.

The images, analysed by Paul Schenk of the Lunar and Planetary Institute in Houston, Texas, and colleagues, reveal two vast craters in Vesta's southern hemisphere. The team calculates that the objects that created these craters - one of which was bigger than the Chicxulub impact thought to have wiped out the dinosaurs - could have scooped out enough material from Vesta to account for all known HED meteorites (Science, DOI: 10.1126/science.1223272).

Rheasilvia is 500 kilometres wide, 20 kilometres deep and sits on top of Veneneia, which is almost as big.

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.